There is a related art image forming apparatus that includes a belt unit (image carrier unit) for conveying a sheet. The belt unit includes a belt stretched between a plurality of rollers, and a frame where the respective rollers are rotatably supported. The frame of the belt unit is pushed against a positioning part, which is provided at an apparatus body, by, for example, a spring member, so that the belt unit is positioned with respect to the apparatus body.
Further, one of the rollers of the belt unit is rotated by a driving force of a belt drive gear that is provided in the apparatus body, and the belt is rotationally driven by the rotation of the roller. Furthermore, photosensitive drums that carry toner images to be transferred to a sheet, a cleaning roller that cleans the belt are provided in the apparatus body while coming into contact with the belt.